Usefulness of a writing device in writer's cramp

Fifteen of 20 patients with writer's cramp treated with a writing device noted an improvement in their writing ability, some quite marked. Despite this benefit, nine patients preferred to use alternate methods. In the absence of adverse effects, we suggest that trials of writing devices be the first recourse for all patients with writer's cramp requiring treatment.     

Hand orthosis as a writing aid in writer's cramp.

Writer's cramp is a focal, task-specific dystonia of the hand and wrist. It primarily affects people who do a significant amount of writing, and causes difficulties in writing. We present five cases with writer's cramp who showed improvement in their writing ability with an applied hand orthosis.     

Reduced parietal connectivity with a premotor writing area in writer's cramp

Writer's cramp is a task‐specific form of dystonia with symptoms characterized by abnormal movements and postures of the hand and arm evident only during writing. Its pathophysiology has been related to faulty sensorimotor integration, abnormal sensory processing, and impaired motor planning. Its symptoms might appear when the computational load of writing pushes a tonically altered circuit outside its operational range. Using resting‐state fMRI, we tested whether writer's cramp patients have altered intrinsic functional connectivity in the premotor–parietal circuit. Sixteen patients with right‐sided writer's cramp and 19 control subjects were studied. We show that writer's cramp patients have reduced connectivity between the superior parietal lobule and a dorsal precentral region that controls writing movements. This difference between patients and controls occurred in the absence of writing and only in the hemisphere contralateral to the affected hand. This finding adds a novel element to the pathophysiological substrate for writer's cramp, namely, task‐independent alterations within a writing‐related circuit. © 2012 Movement Disorder Society     

Cooling improves the writing performance of patients with writer's cramp.

Cooling of hand and forearm muscles by immersion in 15 degrees C cold water for 5 minutes improved the writing performance of patients with writer's cramp. Since abnormal processing of muscle spindle afferent discharges contributes to the pathology of writer's cramp, this effect might result from a reduction in muscle spindle activity by lowering muscle temperature. Cooling is a simple, cheap, and safe procedure, providing temporary relief for patients with writer's cramp.     

Primary writing tremor.

We describe a patient who complained of jerking of the right forearm on writing. Active pronation of his arm produced several beats of pronation/supination tremor. A burst of tremor also could be elicited by tendon taps to the volar surface of the wrist, to the finger extensors, and to pectoralis major, and by forcible supination of the wrist delivered by a torque motor. The subject's writing difficulty and tremor were temporarily abolished by partial motor point anaesthesia of pronator teres. We conclude that the tremor was caused by an abnormal response to muscle spindle input from pronator teres.     

Psychiatric aspects of writer's cramp

Summary Although its aetiopathogenesis is still unknown, writer's cramp is meanwhile regarded essentially an organically induced disorder. However, as shown by this interdisciplinary study, psychodynamic factors should not be neglected. Special attention should be given to the patients' experience of the syndrome and secondary psychoreactive processes.     

Cognitive response control in writer's cramp

Disturbances of the motor and sensory system as well as an alteration of the preparation of movements have been reported to play a role in the pathogenesis of dystonias. However, it is unclear whether higher aspects of cortical - like cognitive - functions are also involved. Recently, the NoGo-anteriorization (NGA) elicited with a visual continuous performance test (CPT) during recording of a 21-channel electroencephalogram has been proposed as an electrophysiological standard-index for cognitive response control. The NGA consists of a more anterior location of the positive area of the brain electrical field associated with the inhibition (NoGo-condition) compared with that of the execution (Go-condition) of a prepared motor response in the CPT. This response control paradigm was applied in 16 patients with writer's cramp (WC) and 14 age matched healthy controls. Topographical analysis of the associated event-related potentials revealed a significant (P < 0.05) NGA effect for both patients and controls. Moreover, patients with WC showed a significantly higher global field power value (P < 0.05) in the Go-condition and a significantly higher difference-amplitude (P < 0.05) in the NoGo-condition. A source location analysis with the low resolution electromagnetic tomography (LORETA) method demonstrated a hypoactivity for the Go-condition in the parietal cortex of the right hemisphere and a hyperactivity in the NoGo-condition in the left parietal cortex in patients with WC compared with healthy controls. These results indicate an altered response control in patients with WC in widespread cortical brain areas and therefore support the hypothesis that the pathogenesis of WC is not restricted to a pure sensory-motor dysfunction.     

Botulinum toxin therapy of writer's cramp

The pathophysiology and management of writer's cramp is one of the most challenging amongst the various forms of focal dystonias. Frequently, the dystonic postures are confounded by compensatory muscle activity. Correct identification of target muscles for botulinum toxin (BT) injections determines the treatment success. The dosages of different preparations vary, with 1 unit of Botox® roughly equalling 3.5 units of Dysport®. Electromyographic guided injections yield better results and may also decrease the amount of toxin required. Weakness of target muscles interfering with other non‐writing activities is a frequently encountered adverse effect. Studies have shown that BT is a safe long‐term therapy option.     

Movement-related cortical potentials in writer's cramp

Movement-related cortical potentials in response to simple, self-paced, brisk index finger abduction movements were recorded in patients with simple and complex writer's cramp and compared with those of age-matched control subjects. Analysis of the movement-related cortical potential waveforms showed that the Bereitschaftspotential, the peak of the negative slope, and the frontal peak of the motor potential did not differ in the two groups, except for the average amplitude of the early part of the negative-slope peak, which was decreased in the patient group during the interval of 300 to 200 msec prior to electromyographic onset. This finding was restricted to the electrodes overlying the contralateral and midline central electrodes. Movement-related cortical potentials from patients and control subjects could be equally accounted for by a four-dipole source model with sources located in the contralateral and ipsilateral sensorimotor regions and the supplementary motor area. There was a trend for a reduction in the strength of the sensorimotor sources active during the premotor period in the patient group, but the difference did not reach a significant level for any individual source. No differences were found between the movement-related cortical potentials elicited by movements of the affected and unaffected hand, or between those of patients with simple or complex hand cramps. This result suggests a deficiency of contralateral motor cortex activation just prior to the initiation of voluntary movements in patients with focal dystonia.     

书写痉挛的立体定向治疗

目的回顾性分析9例书写痉挛患者的立体定向手术治疗的方法及疗效,探讨书写痉挛患者的治疗机制。方法运用脑深部微电极引导下的立体定位技术,对9例药物治疗无效及符合手术指证的书写痉挛患者行丘脑腹外侧核团损毁术,并分析其治疗效果。结果 9例患者即刻恢复书写功能,术后随访,无手术并发症,2³ y的随访中,1例患者复发,余8例患者随访疗效稳定。结论立体定向丘脑腹外侧核团损毁术是书写痉挛的安全有效的治疗手段。     

EMG-EMG coherence in writer's cramp.

We investigated the extent to which oscillatory drives to muscle, believed to arise mainly from the motor cortex, are exaggerated and/or fail to react normally to peripheral stimulation in writer's cramp. We used the coherence between active forearm flexor and intrinsic hand muscles as our index of such drives before and after digital nerve stimulation of the dominant hand. The results in 8 patients with writer's cramp were compared with those in eight age- and sex-matched healthy subjects. We found no significant difference in either the strength of intermuscular coherence or its modulation by cutaneous stimulation between patients and healthy subjects during voluntary flexion of the wrist and extension-abduction of the fingers. Therefore, we were unable to provide evidence for a pervasive disturbance of oscillatory cortical motor outflow in writer's cramp.